Chemistry Topic 7//Hydrocarbons//Fractional Distillation/Cracking of Crude Oil Flashcards

1
Q

What is a HydroCarbon

A

any compound that is formed from Hydrogen and carbon only

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2
Q

What are 3 facts about Alkanes

A
  1. Saturated
  2. Homologous series
  3. C-C single bonds
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3
Q

What is an Alkane

A

A type of HydroCarbon which has C-C single bonds

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4
Q

Why are alkanes Homologous series

A

Because Alkanes are a group of organic compounds that have similar reactivities

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5
Q

Why are Alkanes Saturated

A

Because each carbon atoms forms four single covalent bonds

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6
Q

What is the formula of Alkanes

A

CnH2n+2

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7
Q

What is the first four alkanes and their formula

A

Methane - CH4
Ethane - C2H6
Propane - C3H8
Butane - C4H10

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8
Q

The shorter the carbon chain of HydroCarbons ….

A
  1. The more runny the hydrocarbon is
  2. The more flammable it is
  3. The more volatile it is (turns into gas at lower temp)
  4. lower boiling point
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9
Q

why is shorter chain hydrocarbon in more demand

A

they burn more efficiently (very flammable) and make better fuels than long hydrocarbons

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10
Q

Describe what happens when complete combustion occurs with hydrocarbon

A

complete combustion with hydrocarbon with oxygen releases lots of energy but produces waste product like carbon dioxide and water

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11
Q

What oxidises in this complete combustion of hydrocarbon and oxygen

A

carbon and hydrogen are oxidised and gains oxygen

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12
Q

Why are hydrocarbons used as goof fuels

A

Due to the amount of energy released when they combust completely

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13
Q

What is crude oil

A

made up of different hydrocarbons made over long period of time from remains of plants and animals mainly plankton that can be used as fuels

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14
Q

How is crude oil separated by fractional distillation

A
  1. The oil is heated until majority is turned into gas
  2. Gases enter fractionating column where there is a temperature gradient (hot at bottom and cooler at top)
  3. The longer hydrocarbons have high boiling points and condense back into liquids and drain out
  4. the shorter hydrocarbons have low boiling points and condense and drain out much later on near top where it is cooler
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15
Q

Explain why different fractions exit the column at different points

A

Inside fractionating column is a temperature gradient with hottest part at bottom and coolest at top. when hydrocarbons in the crude oil gas reach a part of the column where the temperature is lower than their boiling point, they will condense and drain out of column

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16
Q

What are the 2 main uses of crude oil

A
  1. Oil provides fuel for transport vehicles
  2. Making of new compounds for use in things like polymers, solvents, detergents and lubricants
17
Q

What is Cracking

A

Thermal decomposition reaction which consists of splitting up long chain hydrocarbons

18
Q

Why is cracking useful

A

Long chain hydrocarbons are useless as they form thick gloopy liquids like tar and instead, short chain hydrocarbons are flammable so make good fuels and in high demand so is useful

19
Q

What does Cracking produce

A

Alkane and Alkenes

20
Q

What are the 2 methods of Cracking

A

Catalytic cracking
Steam cracking

21
Q

Describe Catalytic cracking

A
  1. Apply heat to long chain hydrocarbon to vaporise them
  2. The vapor can be passed over a hot powdered aluminium oxide catalyst
  3. The long chain hydrocarbon splits apart into shorter chain of hydrocarbon made of an alkane and alkene
22
Q

Describe what happens in steam cracking

A
  1. Heat a long chain of hydrocarbon to vaporise them
  2. Then mix them with steam and then heat them to a very high temperature
  3. The long chain hydrocarbon splits apart into shorter chain of hydrocarbon made of an alkane and alkene
23
Q
A